Noise control constitutes a rapidly growing economic and public policy concern for the construction industry. Areas with high acoustical isolation (commonly referred to as ‘soundproofed’) are desirable and required for a variety of purposes. Apartments, condominiums, hotels, schools and hospitals all require rooms with walls, ceilings and floors that reduce the transmission of sound thereby minimizing, or eliminating, the disturbance to people in adjacent rooms. Soundproofing is particularly important in buildings adjacent to public transportation, such as highways, airports and railroad lines. Additionally, facilities such as theaters, home theaters, music practice rooms, and recording studios require increased noise abatement. Likewise, hospitals and general healthcare facilities have begun to recognize acoustical comfort as an important part of a patient's recovery time. One result of the severity of multi-party residential and commercial noise control issues is the widespread emergence of model building codes and design guidelines that specify minimum Sound Transmission Class (STC) ratings for specific wall structures within a building. Another result is the broad emergence of litigation between homeowners and builders over the issue of unacceptable noise levels. In response, to the detriment of the U.S. economy, major builders have refused to build homes, condos and apartments in certain municipalities; and there is widespread cancellation of liability insurance for builders. The International Code Council has established that the minimum sound isolation between multiple tenant dwellings or between dwellings and corridors is a lab certified STC 50. Regional codes or builder specifications for these walls often require STC 60 or more. Such high performance levels are difficult to achieve and field tested designs often fail to perform to the required levels. The problem is compounded when a single wall or structure is value-engineered to minimize the material and labor involved during construction.
One common feature observed in building panels used in walls, ceilings, floors and other construction applications is a notable deterioration of the noise attenuation quality of the panel at low frequencies, particularly at or around 125 Hz. It would be highly desirable to have a building panel that is optimized in sound attenuation and vibration transmission properties such that vibration frequencies from about 50 to about 125 Hz are highly suppressed.
Various construction techniques and products have emerged to address the problem of noise control, but few are well suited to target these selected problem frequencies. Currently available choices include adding gypsum drywall layers, resilient channels and isolated drywall panels, and mass-loaded vinyl barriers with additional drywall panels; or cellulose-based sound board. All of these changes help reduce the noise transmission incrementally, but not to such an extent that identified problem frequencies would be considered fully mitigated (restoring privacy or comfort). Each method broadly addresses the problem with additional mass, isolation, or damping. In other words, each of these is a general approach, not a frequency specific one.
Accordingly, what is needed is a new material and a new method of construction that allows for the maximum reduction of noise transmission at a target frequency of interest, whether it is a low frequency or a high frequency. What is needed is a panel tuned for performance at selected problem frequencies to address the noise encountered in the building acoustics industry.